Configuring a modular storage system

ABSTRACT

Provided is an enclosure for use in a modular storage system, the enclosure comprising a plurality of drive bays, a controller canister, an expansion canister, and a midplane connecting the drive bays to the canisters, wherein the controller canister occupies a greater volume of the enclosure than the expansion canister.

CROSS-REFERENCE TO RELATED FOREIGN APPLICATION

This application is a non-provisional application that claims prioritybenefits under Title 35, United States Code, Section 119(a)-(d) fromUnited Kingdom Patent Application entitled “AN ENCLOSURE” by Ian D.JUDD, having United Kingdom Patent Application Serial No. GB1211918.6,filed on Jul. 5, 2012, which United Kingdom Patent Application isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a modular storage system and a methodfor configuring the modular storage system using two such enclosures.

2. Description of the Related Art

Modular disk storage systems which use rack-mounted enclosures arewidely used in computing. These enclosures are often based on theStorage Bridge Bay (SBB) technology standard. SBB defines a standardelectronics “canister”, in terms of its dimensions, mid-plane signalsand connectors, power supplies and cooling. For example, the IBM®Storwize® V7000 uses enclosures of size 2U that conform to the currentSBB 2.0 standard. Each enclosure provides a number of hot-swap drivebays at the front and two slots for electronics canisters at the rear.The dual canisters provide redundancy to ensure High Availability (HA).The first enclosure is a control enclosure that contains two controllercanisters which run complex software to provide functions like remotecopy, caching, thin provisioning and RAID. Up to nine expansionenclosures can be attached to support additional drives. An expansionenclosure is configured with two expansion canisters. (IBM and Storwizeare registered trademarks of International Business Machines Corp. inthe United States and other countries).

The controller canister is tightly packaged and contains a centralprocessing unit (CPU) complex, host interfaces, a Serial Attached SCSI(SAS) protocol chip and a SAS expander chip. However, an expansioncanister just contains a single SAS expander chip plus a small amount ofmemory. SBB is a very efficient package for mid-range storage systems.However it constrains the CPU, memory and I/O resources which can beprovided in a high-end controller. One option is to lengthen the SBBcanister while keeping the other two dimensions unchanged. This has theadvantage of compatibility with existing enclosures but it only providesa modest increase in card area and it offers no relief on power andcooling. The SBB working group is developing a 3.0 standard which mayincrease the canister height. However packaging two such canisters willprobably require an enclosure of 3U size. Current storage systems havetwo controller canisters in the first enclosure and two expansioncanisters per expansion enclosure. All canisters are the same size, asdefined by the SBB standard.

SUMMARY

Provided is an enclosure for use in a modular storage system, theenclosure comprising a plurality of drive bays, a controller canister,an expansion canister, and a midplane connecting the drive bays to thecanisters, wherein the controller canister occupies a greater volume ofthe enclosure than the expansion canister.

Further provided is a modular storage system comprising: a plurality ofdrive bays; a first enclosure including a first controller canistercoupled to the drive bays and a first expansion canister, wherein thefirst controller canister occupies a greater volume of the enclosurethan the first expansion canister; and a second enclosure including asecond controller canister and a second expansion canister, wherein thesecond controller canister occupies a greater volume of the enclosurethan the second expansion canister.

Further provided is a method of configuring a modular storage systemcomprising: inserting two enclosures into the modular storage system,each enclosure comprising a plurality of drive bays, a controllercanister, an expansion canister, and a midplane connecting the drivebays to the canisters, wherein the controller canister occupies agreater volume of the enclosure than the expansion canister.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described, byway of example only, with reference to the following drawings, in which:

FIG. 1 is a schematic diagram of an enclosure and a canister.

FIG. 2 is a schematic diagram of the interior of an enclosure with twocanisters.

FIG. 3 is a schematic diagram of the rear of two enclosures as known inthe prior art.

FIG. 4 is a schematic diagram of components of a controller canister.

FIG. 5 is a schematic diagram of an embodiment of the rear of twoenclosures.

FIG. 6 is a schematic diagram of an embodiment of the rear of twocanisters showing the SBB midplane connectors.

FIG. 7 is a schematic diagram of an embodiment of a cabinet with twoenclosures therein.

DETAILED DESCRIPTION

According to one embodiment, there is provided an enclosure for use in amodular storage system, the enclosure comprising a plurality of drivebays, a controller canister, an expansion canister, and a midplaneconnecting the drive bays to the canisters, wherein the controllercanister occupies a greater volume of the enclosure than the expansioncanister.

According to a further embodiment, there is provided a method ofconfiguring a modular storage system comprising inserting two enclosuresinto the modular storage system, each enclosure comprising a pluralityof drive bays, a controller canister, an expansion canister, and amidplane connecting the drive bays to the canisters, wherein thecontroller canister occupies a greater volume of the enclosure than theexpansion canister.

With the described embodiments, it is possible to provide an enclosurethat can be used to package one controller canister and one expansioncanister in each of the first two enclosures used in a modular storagesystem and the space in the enclosure is divided asymmetrically, so thatthe controller canister has more space than the expansion canister. Thissignificantly relieves the packaging constraints for high-endcontrollers. The controller canister occupies a greater volume of theenclosure than the expansion canister and this means that more space isavailable for the contents of the controller canister. Rather thanhaving two controller canisters in one enclosure, two enclosures can beused with one controller canister in each of the first two enclosures.The asymmetric use of space, with respect to the canisters, allows thefunctionality of the controller canister to be increased.

FIG. 1 is a schematic diagram (not necessarily to scale) of an enclosure10. This enclosure 10 is shown in perspective from above and behind. Thearrows and attached labels indicate the front and back of the enclosure10. Also illustrated is a canister 12, which is designed to fit into aslot 14 at the rear of the enclosure 10. The backplate 16 of thecanister 12 is also labeled, this will be exposed when the canister 12is fitted into the slot 14 of the enclosure 10. The enclosure 10 of FIG.1 is according to the SBB specification and the canister 12 can beconsidered to be an SBB canister 12 that will fit into an SBB slot 14.

FIG. 1 is designed to show the terminology conventions used whendiscussing the enclosures 10 and the canisters 12. This FIG. 1illustrates the broad principle of an enclosure 10 that has a canister12 fitted therein. The position and number of the canisters 12 withinthe enclosure 10 is variable, depending upon the desired functions andcapabilities of the enclosure 10. The enclosure 10 can be used inmodular storage systems, which are cabinets that have spaces forreceiving enclosures 10, normally in a vertical stacking. Such cabinetsalso provide power and electrical connections and often have their owncomputing functions in order to manage the enclosures 10 containedwithin the cabinet.

The enclosures 10 have a vertical height that is often expressed usingthe unit “U”, so a specific cabinet may be constructed to receiveenclosures of various heights in multiples of 1U. The standardization ofthe cabinets, enclosures and canisters allows different hardwaremanufacturers to provide compatible components that mean that an enduser can mix and match the enclosures as they desire. The enclosures 10are commonly used to provide enterprise storage solutions for largebusinesses for example. A single cabinet will include multipleenclosures 10 which contain disk drives in addition to the canisters 12.The disk drives provide storage solutions for the large amount of datathat is now very common in businesses.

A second embodiment of an enclosure 10 is shown in FIG. 2. This Figureshows the interior of the enclosure 10, which is able to receive two SBBcanisters 12 a, 12 b side-by-side. Again, the arrows and attached labelsindicate the front and back of the enclosure 10. Also shown in this FIG.2 is a midplane 18, which is a physical element to which the canisters12 a, 12 b are connected. The midplane 18 has interconnects 20 whichmate with corresponding interconnects 22 a, 22 b found on the front ofthe canisters 12 a, 12 b. The midplane 18 divides the enclosure intofront and back portions. The front of the enclosure 10 houses the drivebays which support disk drives 24. The disk drives are usually arrangedin one of two different ways in a 2U enclosure, depending on the driveform factor. 2.5″ small-form-factor (SFF) drives are arranged in one rowof twenty-four drives standing on edge. FIG. 2 shows this configuration.3.5″ large form-factor (LFF) drives are arranged in three rows of fourdrives lying flat.

The canisters 12 a, 12 b if they conform to the SBB standard, have theirexternal dimensions defined by the standard and also have the structureand function of their interconnects 22 a, 22 b defined by the standard.An enclosure 10 that wishes to receive SBB canisters must provide slots14 (FIG. 1) of the necessary size and must provide a midplane 18 (FIG.2) that conforms to the physical and functional requirements of thestandard. A canister 12, 12 a, 12 b is any functional entity that can beinserted into a slot 14. The canister 12, 12 a, 12 b is a replaceableunit that comprises an external case with interconnects 22 a, 22 b andinternal electronics. The two canisters 12 a, 12 b of FIG. 2 arenormally identical.

The layout of the enclosure 10 is configured according to themanufacturer's desire, but essentially the drive bays are at the front24 of the enclosure 10, the midplane 18 separates the drive bays fromthe back of the enclosure 10 and the canisters 12 a, 12 b are at theback of the enclosure 10 and are connected to the midplane 18. Thecanisters 12 a, 12 b provide functionality that is either specific tothe enclosure 10 that contains the canisters 12 a, 12 b or one or moreof the canisters 12 a, 12 b provide functionality that is related to allof the enclosures 10 within a cabinet. As discussed above, a typicalcabinet will have multiple enclosures 10 vertically stacked inside thecabinet.

FIG. 3 shows two enclosures 110 a, 110 b that can be used in a modularstorage system such as a cabinet as described above. In a vertical stackof enclosures 110 a, 110 b, the two enclosures 110 a, 110 b shown inFIG. 3 may be the topmost two enclosures 110 a, 110 b in the cabinet.These enclosures 110 a, 110 are configured such that the rear canisters112 a ₁, 112 a ₂, 112 b ₁, 112 b ₂ are arranged vertically one above theother (rather than horizontally side-by-side as shown in FIG. 2, forexample). Each enclosure 110 a, 110 b is also provided with two powersupplies 126 a ₁, 126 a ₂, 126 b ₁, 126 b ₂ and cables 128 a, 128 bconnect together canisters 112 a ₁ and 112 b ₁ and 112 a ₂ and 112 b ₂in different enclosures 110 a, 110 b. The two enclosures 110 a, 110 bare the same size, having a vertical height of 2U and the variouscanisters 112 a ₁, 112 a ₂, 112 b ₁, 112 b ₂ are all the same size.

The enclosures 110 a, 110 b conform to the current SBB 2.0 standard andare of size 2U. Each enclosure 110 a, 110 b provides hot-swap drive baysat the front and has two slots for the SBB canisters 112 a ₁, 112 a ₂,112 b ₁, 112 b ₂ at the rear. The dual canisters 112 a ₁, 112 a ₂, 112 b₁, 112 b ₂ provide redundancy to ensure so-called high availability. Theupper enclosure 110 a is a control enclosure that contains twocontroller canisters 112 a ₁, 12 a ₁ which run complex software toprovide functions such as remote copy, caching, thin provisioning andRAID. The lower, expansion enclosure 110 b can be attached to supportadditional drives, as can subsequent additional expansion enclosures 110b. Each expansion enclosure 110 b is configured with two expansioncanisters 112 b ₁, 112 b ₂.

The construction of the enclosures 110 a, 110 b and the nature of theSBB standard create a constraint on the high-end controller packing ofthe controller canister 112 a _(i), 112 a ₂. Equally, the expansioncanisters 112 b ₁, 112 b ₂ have far more space than is needed for actualelectronic components that are carried in an expansion canister 112 b ₁,112 b ₂. The upper control enclosure 110 a is provided with twocontroller canisters 112 a ₁, 112 a ₂ in order to provide redundancy inrelation to the functions provided by the canisters 112 a ₁, 112 a ₂.For much the same reason that there are two power supplies 126 a ₁, 126a ₂, 126 b ₁, 126 b ₂ in each enclosure 110 a, 110 b, the two controllercanisters 112 a ₁, 112 a ₂ are able to duplicate their function so thatshould one of the canisters fail, then the other will still beavailable.

FIG. 4 shows the internal components of a controller canister 200, suchas canisters 112 a ₁, 112 a ₂. The CPU complex runs the controller code.It contains a CPU 202, memory 204, Platform Controller Hub 206,Baseboard Management Controller (BMC) 208, Ethernet management ports(GbE) 210 a, 210 b, a Solid State Disk (SSD) 212 for the boot device anda BIOS 214. The memory 204 is packaged on two Very Low Profile (VLP)Dual Inline Memory Modules (DIMMs). The CPU 202 also provides a numberof PCI Express lanes for I/O. These are connected via a PCI Expressswitch 218 to a Fibre Channel (FC) chip 220 for the host interface, anoptional Host Interface Module (HIM) 222 for additional host ports and aSAS controller chip 224. The PCI Express 218 switch also contains aNon-Transparent Bridge (NTB) 226 for the link which connects to the peercontroller via the midplane. The SAS controller 224 attaches to a SASexpander 228 which connects to the internal drive slots via the midplaneand an external connector for expansion enclosures. The SAS expander 228also contains an embedded CPU core to manage the enclosure and drives.

By contrast, an expansion canister 112 b ₁, 112 b ₂ will only have asubset of the components shown in FIG. 4. An expansion canister 112 b ₁,112 b ₂ will only need to have the SAS expander 228 and its associatedmemory chips, the Flash 230, NVRAM 232 and RAM memory 234 components.The SAS expander 228 connects to the internal drive slots via themidplane and two external connectors. The upstream connector is cabledto the previous control or expansion enclosure in a chain. Thedownstream connector is cabled to the next expansion enclosure. The SASexpander 228 also contains an embedded CPU core to manage the enclosureand drives.

FIG. 5 shows an improved design of the enclosure and canisters. Theenclosures 310 a, 310 b of FIG. 5 are still a standard 2U vertical sizewith a plurality of drive bays at the front of the enclosures 310 a, 310b and a midplane 18 separating the drive bays from the back of theenclosure 310 a, 310 b, with a controller canister 300 a, 300 b at theback of the enclosure 310 a, 310 b and connected to the midplane 18, andan expansion canister 302 a, 302 b at the back of the enclosure 310 a,310 b and connected to the midplane 18 but the controller canister 300a, 300 b occupies a greater volume of the enclosure 310 a, 310 b thanthe expansion canister 302 a, 302 b.

Essentially, the two canisters 300 a, 302 a and 300 b, 302 b used in theenclosures 310 a, 310 b, respectively, are of an asymmetric size. In theconfiguration of FIG. 5, the controller canisters 300 a, 300 b have agreater vertical height than the expansion canisters 302 a, 302 b, allother measurements being equal. The vertical height within the enclosure310 a, 310 b is not split 50/50 between the two canisters 300 a, 300 band 302 a, 302 b as in the prior art design of FIG. 3. The controllercanister 300 a, 300 b is larger than the expansion canister 302 a, 302b. This increases the volume available to the contents of the controllercanister 300 a, 300 b and this means that either additional componentscan be used in the controller canister 300 a, 300 b or cheaper versionsof the components can be used.

The solution of FIG. 5 puts one controller canister 300 a, 300 b in eachof first two enclosures 310 a, 310 b used in a cabinet. This allows eachcontroller canister 300 a, 200 b to use a larger share of enclosure 310a, 310 b resources and provides more space for host interface modules,CPU heatsink and battery backup. There is no need for very low profile(VLP) DIMMs when using stacked canisters. More power and cooling can beprovided to the components of the controller canister 300 a, 300 b. Theinter-controller links in the midplane 18 are replaced with anadditional PCIe cable 334. The reduction in size of the expansioncanister 302 a, 302 b has no impact on its cost or function.

FIG. 6 shows a rear view 300 of two canisters 300 and 302, such ascanisters 300 a, 300 b and 302 a, 302 b, in an improved enclosure 310,such as 310 a, 310 b. The SBB midplane connectors M1 to M9 are viewedfrom the rear of enclosure. The lower canister 302 is upside down inthis product, which places the midplane connectors of the two canisters300 and 302 further apart. A printed circuit board 306 is shown for thecontroller canister 300 and a printed circuit board 308 is shown for theexpansion canister 302. Respective latches 340 and 342 are also shownfor the controller canister 300 and the expansion canister 302.

The different sizes of the canisters 300 and 302 result in an asymmetriccontroller canister 300 that is 14 mm higher than the current prior artcontroller canister 12 a. Correspondingly, the expansion canister 302 is14 mm shorter in its vertical height. The controller canister 300occupies a greater volume of the enclosure than the expansion canister302. The resulting larger controller canister 300 is therefore able toaccommodate standard 30 mm low-profile DIMM's with 3 mm to spare andsupports the use of two HIMs on the same riser using low-profile PCIecards. A single HIM has a restricted component height, ˜10 mm versus14.47 mm in PCIe standard. There is a requirement to reposition theenclosure spigot for the controller latch 340.

The table below provides a comparison of the prior art symmetric designof canisters with the improved asymmetric design of canisters.

Improved Prior art (symmetric) (asymmetric) Max controller power 2 × 175Watts 300 Watts (+ 50 W expansion) Max CPU power 65 Watts 95+ Watts Maxmemory with 4 Gbit 32 GB 64 GB chips (4 VLP DIMMs) (4 LP DIMMs) Rearpanel area for 77 square cm. 106 square cm (1.38x) connectors Hostinterface modules 1 2 on same riser (PCIe low-profile cards) (1restricted to 10 mm component height) Battery Difficult to packageEasier to package within the canister internally Minimum HA 1 enclosure2 enclosures configuration

As can be seen from the above, the use of the asymmetric design hasnumerous advantageous features when compared with the prior artsymmetric design, all of which stem from the increased size of thecontroller canister 300. If a high availability configuration is beingused (final row of the table), then two enclosures 310 a, 310 b will beneeded in the cabinet to provide two individual controller canisters 300a, 300 b. FIG. 7 illustrates a modular storage system (not to scale)being a cabinet 344 with its door 346 open which includes two enclosures310 a, 310 b, where each enclosure 310 a, 310 b is utilizing theasymmetric canisters 300 and 302 described above.

The table above shows the advantages of the asymmetric arrangement ofcanisters over current SBB designs. The table assumes a layout such asthe IBM Storwize V7000 with the two canisters stacked one above theother, as shown in FIG. 6. Some enclosures have an alternative layoutwith the canisters side-by-side across the full width of the enclosure,as shown in FIG. 2, and the power supplies are underneath. In this case,the improved design increases the controller card area but not thecanister height. Most of the advantages still apply except that it wouldnot be possible to use standard low-profile DIMMs.

What is claimed is:
 1. An enclosure for use in a modular storage system,the enclosure comprising: a plurality of drive bays, a controllercanister, an expansion canister, and a midplane connecting the drivebays to the canisters, wherein the controller canister occupies agreater volume of the enclosure than the expansion canister.
 2. Theenclosure of claim 1, and further comprising two power supplies eachconnected to the controller canister and the expansion canister.
 3. Theenclosure of claim 1, wherein the controller canister includes aninternal battery.
 4. The enclosure of claim 1, wherein the controllercanister has a greater vertical height than the expansion canister. 5.The enclosure of claim 1, wherein the controller canister and theexpansion canister are side-by-side.
 6. The enclosure of claim 1,wherein the controller canister and the expansion canister are stackedin a vertical orientation with the controller canister stacked above theexpansion canister.
 7. The enclosure of claim 1, wherein the controllercanister and the expansion canister each have an upper end and a lowerend with respect to the vertical orientation in which the controllercanister and the expansion canister are stacked, wherein a printedcircuit board of the controller canister is positioned at the upper endof the controller canister and a printed circuit board of the expansioncanister is positioned at a lower end of the expansion canister.
 8. Theenclosure of claim 1, wherein the expansion canister includes a subsetof components included in the controller canister.
 9. A modular storagesystem comprising: a plurality of drive bays; a first enclosureincluding: a first controller canister coupled to the drive bays; and afirst expansion canister, wherein the first controller canister occupiesa greater volume of the enclosure than the first expansion canister; anda second enclosure including: a second controller canister; a secondexpansion canister, wherein the second controller canister occupies agreater volume of the enclosure than the second expansion canister. 10.The modular storage system of claim 9, wherein the two controllercanisters, one in each enclosure, are connected by an external cable.11. The modular storage system of claim 9, wherein the first and secondcontroller canisters has a greater vertical height than the first andsecond expansion canisters, respectively.
 12. The modular storage systemof claim 9, further comprising: two power supplies in each of the firstand second enclosures, wherein the first controller canister and firstexpansion canister share the two power supplies in the first enclosureand the second controller canister and the second expansion canistershare the two power supplies in the second enclosure.
 13. The modularstorage system of claim 9, wherein in the first enclosure, the firstcontroller canister and the first expansion canister are stacked in avertical orientation with the first controller canister stacked abovethe first expansion canister and wherein in the second enclosure, thesecond canister and the second expansion canister are stacked in thevertical orientation with the second controller canister stacked abovethe second expansion canister.
 14. The modular storage system of claim13, further comprising: a cabinet including a door having a first shelfin which the first enclosure is disposed and a second shelf in which thesecond enclosure is disposed.
 15. A method of configuring a modularstorage system comprising: inserting two enclosures into the modularstorage system, each enclosure comprising a plurality of drive bays, acontroller canister, an expansion canister, and a midplane connectingthe drive bays to the canisters, wherein the controller canisteroccupies a greater volume of the enclosure than the expansion canister.16. The method of claim 15, wherein each enclosure further comprises twopower supplies each connected to the controller canister and theexpansion canister.
 17. The method of claim 15, wherein the controllercanister of each enclosure includes an internal battery.
 18. The methodof claim 15, wherein the controller canister of each enclosure has agreater vertical height than the expansion canister.
 19. The method ofclaim 15, wherein the controller canister and the expansion canister ofeach enclosure are side-by-side.
 20. The method of claim 15, furthercomprising connecting the two controller canisters, one in each of theenclosures by an external cable.